Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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359 FXUS61 KPHI 280327 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1127 PM EDT SAT AUG 27 2016 .SYNOPSIS... High pressure centered over southern Quebec this afternoon will drift to the east. The high will continue to influence our weather into Sunday. A frontal boundary approaching from the northwest is forecast to arrive during the afternoon and evening hours on Monday. The front is expected to stall and slowly dissipate on Tuesday on Wednesday. A cold front from the northwest is anticipated to pass through our region early on Thursday followed by high pressure for Friday and Saturday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Surface high pressure ridge axis will be just northwest of I-95, maintaining a low-level easterly flow near and to the southeast of this area. Temperature-Dewpoint depressions over the southern two thirds of Delaware and portions of southeast New Jersey have decreased significantly this evening. A general consensus of the short range guidance indicates the surface layer will saturate, under a strong radiation (long wave cooling) inversion, as skies clear from resultant large scale subsidence within the mid level ridge. We expect winds to decouple just enough over portions of Delaware and southern NJ to allow patchy fog to develop. Given the dry low level air in place above the developing radiation inversion, as evidenced by the absence of low clouds offshore in the last visible satellite of the day, we do not expect much in the way of low cloudiness to develop overnight. Interestingly, the warmer than normal Sea Surface Temperatures (SSTs) may be playing a role in this. The main change with this update was to add patchy fog for the aforementioned areas. We also made some minor updates both the overnight temperatures and dew points. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... High pressure will continue to influence our weather for Sunday. Any patchy fog will clear early in the morning and another relatively sunny day will had across the region. Easterly winds will be light through the day, around 10 mph or less. Temperatures will be similar to today, with highs into the mid to upper 80s to around 90 across the region. With an easterly flow in place, shore points will be slightly cooler and remain in the upper 70s to lower 80s. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... A mid level short wave trough is anticipated to move across New York State and New England during the afternoon and evening hours on Monday. It should push a surface frontal boundary into our region at that time. The guidance continues to suggest only a limited potential for precipitation. A band of precipitable water values around 1.7 inches is forecast to precede the front and there should be marginal instability. We will keep the mention of a slight chance of showers and thunderstorms. It appears as though the boundary will dissipate slowly over or near Maryland, Delaware and southern New Jersey. Drying is expected to work its way into our region from the north for Tuesday so we are not anticipating any precipitation at that time. Temperatures are forecast to remain above normal for Monday, Tuesday and Wednesday with highs around 90 and lows ranging from the middle 60s to the lower 70s. Readings will be lower than those values in the elevated terrain of the Poconos and northwestern New Jersey. A cold front is expected to approach from the northwest on Wednesday. It looks as though our best chance of showers and thunderstorms during the coming week will be on Wednesday afternoon into Wednesday night in advance of the front. The boundary should pass through our region early on Thursday. High pressure is forecast to build from Ontario and the Great Lakes on Thursday to the northeastern states on Saturday. The air mass will be noticeably cooler and less humid than the one that it will be replacing. && .AVIATION /04Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Overnight...Predominantly VFR conditions. Easterly winds will decrease to less than 5 knots at most locations. Latest guidance indicates that patchy fog will be the primary concern, mainly at ACY and MIV. There could also be some low clouds at these sites, and we added SCT005 to SCT007, as conditions are not favorable for the development of widespread low clouds. Sunday...Predominantly VFR conditions. Light southeast winds around 10 knots or less. OUTLOOK... Sunday night through Wednesday morning...Mainly VFR. Late night and early morning visibility restrictions are possible. Wednesday afternoon into Wednesday night...Mainly VFR. However, there is a chance of showers and thunderstorm. Thursday...Mainly VFR. && .MARINE... Sub-advisory conditions are expected to continue on the area waters through Sunday. Easterly winds around 10 to 15 knots across the area waters. Seas around 2 feet tonight, increasing to 2 to 4 feet on Sunday as we start to see the swells arrive from distant Tropical Storm Gaston. OUTLOOK... Sunday night through Thursday...No marine headlines are anticipated. RIP CURRENTS... A moderate risk for the formation of dangerous rip currents is forecast for Sunday along the NJ shore and Delaware beaches. East-northeast winds are expected to increase during the day, with waves in the surf zone building 3 to 4 feet. A dominant, longer period swell around 10 seconds, is also anticipated to to reach the coast later in the day. Low tide occurs late in the morning, and the rip current risk may be attenuated into the early afternoon. Complicating matters, the long period swells from Tropical Cyclone Gaston should arrive late Sunday as the cyclone nears 55 degrees west longitude. However, the long period 12 to 15 second swells are forecast to become more pronounced along the coasts of New Jersey and Delaware on Monday and Tuesday, even as Gaston makes its turn northeast. Momentum in the swells reaching our coast due to the original westward motion of the tropical system should result in an enhanced threat for the development of dangerous rip currents for much of the week. Presuming these swells occur as outlined above, this will eventually impact beach behavior. Follow the advice of local lifeguards who will be observing and your safety net. This is not a time to swim on your own without lifeguard presence. Additionally waders are cautioned not to turn their backs to the waves when coming out of the water. Wave knock down can result in upper torso injury. && .CLIMATE...
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This section is up to date through 11 PM this Saturday evening August 27. A top 4 warmest August appears assured most of our forecast area with record monthly warmth likely at PHL. A top 3 warmest June-July-August for Philadelphia, Allentown and possibly Atlantic City. Philadelphia is on its way for its warmest August on record (dating back to 1874). More than 4 degrees above normal. This Philadelphia August ranking includes our forecast temps (SFT specific values) through the 31st. The 30 year normal is 76.6 Records date back to 1874. 1. ~81.0 2016 2. 79.9 1980 3. 79.8 2001 and 1995 Regarding whether August can tie its record of 17 90F days. Its possible but not probable. Foresee an additional 3 to 4 more 90 degree days to add onto the 13 we have so far this month. The record of 17 was set in 1995. The mean for the month is only 5. Allentown will probably rank #2 warmest August. Records date back to 1922. Normal is 71.7 and we are projecting a positive departure of around 5 degrees. 1. 78.2 1980 2. 76.7 2016 3. 76.0 1937 Atlantic City records date back to 1874. The August monthly normal is 74.4 and we`re projecting a positive departure of nearly 4 degrees. As it stands, Atlantic City will rank #1 or #2 warmest August with very little chance of slipping to #3. The forecast and climate for Atlantic City has greater variability than Allentown and Philadelphia due to proximity to water on sea breeze days and notable radiational cooling on some nights. 1. 78.2 2016 2. 77.9 2005 3. 77.1 2009 Seasonal: This summer 2016 for Philadelphia will probably be the 2nd warmest June-July-August (JJA) in the period of record dating back to 1874. 1. 79.6 2010 2. 78.9 2016 3. 78.6 1995 4. 78.3 1994 Allentown seasonal avg is projecting 75.0 or a ranking of around #2 in the por. 1 75.3 1949 2 75.0 2016 3 74.6 2005 and 1980 Atlantic City seasonal average is projecting 75.8...4th warmest in the por. 1. 77.5 2010 2. 77.0 2011 3. 75.9 2005 4. 75.8 2016 5. 75.5 2008 90 degree days through the 27th. season mean Aug Aug Aug Season mean rer rer abe 32 17 11 4 16-1980 41-1966 acy 27 10 10 3 11-2010 46-2010 phl 37 21 13 5 17-1995 55-2010 ilg 32 20 13 5 23-1895 59-1895 Rainfall: Uncertainty exists below. Presuming no further measurable rain this month of August...the current ACY value of 1.10 would rank the 6th driest August on record, after a 6th wettest July. For Philadelphia, the June-August seasonal total of 7.45 inches is the 12th driest summer...again this presumes no further measurable rain in August.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Franck/Iovino Near Term...Franck/Meola Short Term...Meola Long Term...Iovino Aviation...Franck/Iovino/Meola Marine...Franck/Iovino/Meola Climate...Drag 1127P is the U.S. government's official web portal to all federal, state and local government web resources and services.